Electric draft control gauge



Dec. 22, 1942.

M. w. CREW ELECTRIC DRAFT CONTROL GAUGE Tiled Anri INVENTOR MORRIS W.CREW BY ATTORNE 6 Patented Dec. 22, 1942 ELECTRIC DRAFT CONTROL GAUGEMorris W. Crew, Shaker Heights, Ohio, assignor to The Hotstream HeaterCompany, Cleveland, Ohio, a corporation of Ohio Application April 19,1941, Serial No. 389,305

6 Claims.

This invention relates to improvements in control instruments andespecially to apparatus for actuating control switches in response tovariations in draft or pressure.

One of the objects of the present invention is to provide novel meansfor making and breaking electric circuits in response to movements of aflexible diaphragm.

Another object of the present invention is to provide an oscillating armindicating variations of draft or pressure and a fixed arm adapted to beset at a predetermined point in the range of draft or pressurevariation, and a control device actuated by relative movement betweenthe arms. More particularly an oscillating disk is mounted on themovable arm as an axis and this disk is abutted by the fixed arm at apoint spaced from the center of the disk so that relative movementbetween the arms causes rotation of the disk and actuation of a mercuryswitch carried by the disk.

Other objects and advantages will appear from the accompanying drawingsand description and the essential features thereof will be summarized inthe claims.

In the drawing, Fig. 1 is a front elevation of a device embodying myinvention with the front of the casing removed so as to better show theparts; Fig. 2 is a sectional view through the same taken along the line2-2 of Fig. 1 and with the front of the casing in position; Fig. 3 is afragmental sectional view similar to the upper portion of Fig. 2 andshowing another position of the parts; Fig. 4 is an enlarged fragmentalsectional view taken along the line 4--4 of Fig. 1; while Fig. 5 is awiring diagram illustrating one use of my device.

As shown in the various views, within a casing ID is mounted a basemember I l forming a pressure chamber, the top of which is closed by aflexible diaphragm l2 held upon the base member by means of the frame orring it. Mounted on the base member as by means of pedestal members [4is a U-shape bracket l5 having front and rear parallel bracket armsrigidly connected together by the spacer bar H3.

At the upper end of the rear arm of bracket I5 is mounted a stud H inthe free end of which is inserted a stub shaft 18 as best seen in Fig.4. Pivotally mounted on this shaft is an arm I!) on the outer end ofwhich is oscillatably mounted a disk 20 which oscillates about the armI9 as an axis. Mounted on the face of this disk are mercury switches 21and 22. As best seen in Figs. 2 and 3, switch 2| makes connection of itselectric contacts when the mercury of the bulb is tilted toward theright-hand end thereof and bulb 22 makes contact when the mercurythereof is tilted toward the left-hand end thereof. The contacts ofthese switches are connected by very flexible wires to binding posts 23,24, 25 and 26.

A pointer 21 moves with the arm l9'across a scale 28 carried on dial 29which is mounted on the front arm of bracket [5. A link 30 has a clevisconnection at 3011 with the arm l9 and is suitably connected at itslower end with the diaphragm I2. Thus vertical movement of the diaphragmcauses oscillation of arm IS. A counterweight 3i balances arm l9, disk2|], switches 2| and 22 and the connection 30 about the axis l8.Counterweight 32 balances pointer 21 so that with these parts and noothers connected the pointer 2'! would remain in practically anyposition to which it was moved. A rod 33 rigid with arm H! extendsvertically downward when the pointer 21 is at zero on its scale and apendulum weight 34 tends to hold the pointer in zero position, andmovement of the diaphragm l2 and the pointer 2! in response to changesin draft is opposed by the weight 34. This portion of the instrumenttherefore provides a very delicately balanced, practically frictionlessindicating device giving accurate indications over the scale 28 and notrequiring the use of any springs.

Another arm 35 is pivotally mounted on shaft I3 and extends outwardlysubstantially parallel to arm l9 where the free end of this arm passesthrough a slot 20a in the disk 20. On the other side of shaft l8 thisarm is pivotally connected at 36 by means of a clevis 31 and a rod 33with an adjusting knob 39 on the outside of the easing [0. By means ofsaid adjusting knob 39 the position of arm 35 is fixed. A pointer 42movable with arm 35 indicates on scale 28 the point selected which isthe draft or pressure to be maintained by the instrument.

A wiring board 4| is secured to the rear arm of bracket l5 and carriesthe binding posts previously described and also the posts 42 and 43 towhich an outside source of electricity may be connected, and bindingposts 44, 45 and 4b to which a controlling motor or the like may beconnected. On the front wall of the casing ID may be mounted a controlknob 47 for controlling a switch blade 41a. which may have severalsettings as indicated diagrammatically in Fig. 5. In other words thereis a position for automatic control which is the setting shown in Fig.5; there is another setting for maximum movement of the control device;another one for minimum movement of the control device; and an "offposition of the switch.

One use which I contemplate for my device is the control of a draftdamper by a device connected to the posts 44, 45 and 46 so as tomaintain a predetermined draft as set by the pointer 40. This draft willbe measured in the pressure chamber II and will be indicated at thepointer 21. Variations of the pointer 21 away from the pointer willindicate variations of the draft from that which is desired and thesesame variations will cause relative movement between the arms I9 and 35.Obviously with the parts in the position indicated in Fig. 2 there is nocontact at either of the mercury switches and no movement of the controldevice is called for. However upon' movement of arm 59 in acounterclockwise direction from the position shown in Fig. 1 the partswill move as indicated in Fig. 3 because of the fixed arm 35 engaging inthe slot 20a. As the arm [9 carries the center of disk 20 downwardly asviewed in Fig. 3, the disk is caused to rotate Slightly making contactat the right-hand end of switch 2|. This causes a flow of electricity asfollows in Fig. From L1 and binding post 42 through line 48, switch4111, line 49, binding post 24, switch 2|, binding post 23 and lines 55and 5| to binding post 44. L2 is already connected through post 43 andline 52 with post 45. Thus one circuit of the control device connectedbetween posts 44 and 45 is energized to cause a suitable movement of thecontrol damper or the like thus tending to bring the draft in chamber 1I back to the desired point so as to again return switches El and 22 totheir neutral position. If draft varies in the opposite direction tothat just described so as to cause oscillation of disk 20 in acounterclockwise direction from that shown in Fig. 2, then contacts willbe broken in switch 2| and will be closed in switch 22. This causes acircuit from L1 through line 48, switch 47a, lines 49 and 53 to bindingpost 25 through switch 22, binding post 26, lines 54 and 55 to bindingpost 46. This will energize the circuit of the control devices incircuit between binding posts 45 and 46 so as to move it in the oppositedirection from that which occurs when the circuit is between bindingposts 44 and 45. This will again correct the undesirable condition inpressure chamber l I so as to return arm l9 to its position parallel toarm 35 with the pointers 21 and 40 in registration. This device is sosensitive that movement of the arms corresponding to a variation of oneor two one-hundredths of an inch of water column is suflicient to causeactuation of the device.

Obviously by adjustment of knob 39, arm 35 may be moved to differentpositions corresponding to a different draft which it is desired tomaintain and this automatically sets the neutral position of disk 20 sothat the device will tend to hold that neutral position because, asabove described, every movement of disk 20 caused by a variation of arm19 away from parallelism with arm 35 will bring about its own adjustmentso as to return the parts to the predetermined draft control position.

Referring again to Fig. 5, it wil: be noted that the maximum button isconnected by lines 55 and 55 to the binding post 46 and the minimum,button is connected by lines 57 and 51 to binding post 44. Thus wheneverswitch 41a is moved to the maximum or minimum buttons the control devicemoves as far as possible in either of its two directions of movement asselected by the knob 41.

While I have described my device as used in the control of draft, itwill be understood that it may be used to control pressure also bysubstituting for the link 35 a suitable pressure connection such as isdisclosed in my copending application Serial No. 383,965, filed March18, 1941.

What I claim is:

l. A control gauge comprising means responsive to a medium to becontrolled, an arm oscillatable about a point on said arm by said means,a plate oscillatable about said arm as an axis, an

arm engaging said plate at a point spaced from the center thereof, meansfor setting said arm in various adjusted positions, and a control memberactuated by movement of said plate responsive to relative movementbetween said arms.

2. A control gauge comprising means responsive to a medium to becontrolled, an arm oscillatable by said means, a plate oscillatableabout said arm as an axis, a settable arm engaging said plate at a pointspaced from the center thereof, and a mercury bulb switch on said platesubstantially at right angles to said arm and having contacts connectedand disconnected by mercury flow in said bulb responsive to relativemovement between said arms.

3. A control gauge comprising means forming a pressure chamber andhaving a flexible diaphragm wall, an oscillatable shaft, an arm fixedthereto, connecting means for oscillating said shaft responsive tomovement of said diaphragm wall, a disk oscillatable about said arm asan axis, two mercury switches positioned on said disk and havingcontacts of one closed and contacts of the other opened by diskoscillation, and a fixed abutment contacting said disk at a point spacedfrom its axis.

4. A control gauge comprising means forming a pressure chamber andhaving a flexible dia phragm wall, an oscillatable shaft, an arm fixedthereto, connecting means for oscillating said shaft responsive tomovement of said diaphragm wall, a disk on said arm spaced from saidshaft, said disk being oscillatable about said arm as an axis, a mercuryswitch on said disk and adapted to have its contacts opened and closedby disk oscillation, a pointer oscillatable by said shaft,

means counterweighting said arm and said connecting means and said diskand switch and pointer so that these parts are in balance about saidshaft, a second arm extending radially from said shaft, a pendulumweight on said second arm, and a fixed abutment contacting said disk ata point spaced from its axis.

5. A control gauge comprising means forming a pressure chamber andhaving a flexible diaphragm wall, an oscillatable shaft, an arm fixedthereto, connecting means for oscillating said shaft responsive tomovement of said diaphragm wall, a disk on said arm spaced from saidshaft, said disk being oscillatable about said arm as an axis, a mercuryswitch on said disk and adapted to have its contacts opened and closedby disk oscillation, means counter weighting said arm and saidconnecting means and said disk and switch so that these parts are inbalance about said shaft, a second arm extending radially from saidshaft, a pendulum weight on said second arm, and a fixed abutmentcontacting said disk at a point spaced from its axis.

6. A control gauge comprising means forming a pressure chamber andhaving a flexible diaphragm wall, an oscillatable member, connectingmeans for oscillating said member responsive to movement of saiddiaphragm wall, a member fixed relative to said oscillatable member,means for holding said last named member in various adjusted positions,a disk carried by said oscillatable member, said disk being oscillatableabout an axis, means connected with said fixed member abutting said diskat a point spaced from the axis thereof, whereby said disk is oscillatedby relative movement between said members, and a control memberresponsive to disk oscillation.

MORRIS W. CREVI.

